Peripheral nervous system (PNS) myelin is a differentiated form of Schwann cell plasma membrane rich in glycoproteins. These glycoproteins may be crucial for myelin formation and maintenance, and may play a prominent role in the pathogenesis of acquired demyelinative neuropathies. The proposed study will characterize an abundant, previously undescribed, high molecular weight PNS myelin glycoprotein (Mr 170,000) by isoelectric focusing, peptide mapping and analysis of carbohydrate components. Polyclonal and monoclonal antibodies directed against this glycoprotein will be raised and used for immunoperoxidase and immunofluorescence studies to localize the protein in immature and mature PNS myelin as well as to analyse its metabolism in vivo and in cultured Schwann cells. Further studies are planned to facilitate recognition of PNS myelin glycoproteins with functional or disease-related significance which warrant intensive characterization. These studies will include a search for; 1) glycoproteins that are induced early in the process of myelination; 2) glycoproteins altered in characteristics or quantity in nerves demyelinated by intraneural administration of the potent glycosylation inhibitor, tunicamycin (a treatment previously demonstrated to produce a severe, purely demyelinative neuropathy); and 3) glycoproteins that bind antibodies present in the sera of patients with the Guillain-Barre syndrome.